Adsorption of CO on various M@Pt core–shell nanoparticles: Surface-enhanced infrared absorption and DFT studies

Addition of some other metals to platinum causes significant increase of its catalytic activity towards ethanol electrochemical oxidation. This may be caused by different adsorption of CO molecules on the surface of the catalyst, and hence different resistance of the M@Pt nanostructures to poisoning by CO. In this work we attempt to verify this hypothesis analyzing vibrational spectra of CO adsorbed on various metal nanoparticles. Au@Pt nanoparticles revealing significantly higher catalytic activity towards ethanol oxidation than one-element Pt nanoparticles have been synthesized. Surface-enhanced infrared absorption (SEIRA) spectra of CO adsorbed on Au@Pt and Pt nanoparticles have been measured. Obtained spectra were very similar, which suggests that the higher catalytic activity of Au@Pt nanoparticles is rather not caused by different adsorption of CO molecules on Pt and Au@Pt nanoparticles. We suppose that better performance of core–shell M@Pt nanoparticles than one elements Pt nanoparticles towards ethanol electrochemical oxidation can be explained as follows: core–shell nanoparticles are probably much more defected than one-element nanoparticles, hence the M@Pt nanoparticles posses greater number of active sites (kinks, adatoms, and so on) for ethanol electrochemical oxidation. Analysis of the catalytic activity and CO adsorption have been also carried out for other nanoparticles including: Sn@Pt, Pb@Pt, Pd, Au@Pd, Sn@Pd and Pb@Pd. Density functional theory (DFT) calculations of CO modes for CO adsorbed on tetrahedral Pt10 or Pd10 clusters with different metal–metal distance have been also performed.